This invention relates to enzymes having chorismate mutase and/or prephenate dehydratase activity, and their use in the production of desired compounds such as phenylalanine.
The phenylalanine synthesis pathway in microbes is known to include reactions catalyzed by a single dual-function enzyme, or two separate enzymes, having chorismate mutase and prephenate dehydratase (CMPD) activity. Generally, this activity is subject to feedback inhibition from phenylalanine. Escherichia coli have a chromosomal gene encoding CMPD activity, termed pheA.
Tribe, Australian Published Application No. 72727/81 discloses an E. coli mutant termed NST37 said to produce chorismate mutase prephenate dehydratase substantially free from inhibition by phenylalanine.
Hudson and Davidson, J. Mol. Biol. 180: 1023-1051 (1984), disclose the nucleotide sequence of E. coli pheA.
Baldwin et al., Arch. Biochem. Biophys. 211: 66-85 (1981), disclose that increasing phenylalanine concentration converts dimeric CMPD to inactive tetramers and octamers.
Gething and Davidson, Eur. J. Biochem. 86: 159-164 (1978), disclose that changes in the CMPD aggregation state do not induce gross secondary structural changes, and when CMPD is exposed to phenylalanine, a tryptophanyl residue moves into a more hydrophobic microenvironment.
Gething and Davidson, Eur. J. Biochem. 86: 165-174 (1978), disclose that modification of CMPD cysteinyl residues with 5,5-dithiobis[nitrobenzoate] desensitizes CMPD to phenylalanine feedback inhibition.
Gething and Davidson, Eur. J. Biochem. 78: 111-117 (1977), disclose that modification of the two tryptophanyl residues of CMPD, using dimethyl[2-hydroxy-5-nitrobenzyl sulphonium bromide], results in a partially active, feedback resistant enzyme.